Ga - Early Human Development Ii - Fertilization And Cleavage

Front 1

Corpus Luteum - what is it, what does it secrete, what does it do

Back 1

-Remnants of mature follicle become corpus luteum
-Granulosa and thecal cells differentiate (luteinize), forming apparatus for steroid biosynthesis
-Secretes Progesterone
-Supports endometrial changes favorable to implantation

Front 2

Fertilization - when does spermatozoa meet ovum complex, where does it occur, spermatozoon locking

Back 2

-Within about 24 hours of ovulation, spermatozoa meet ovum complex
-Fertilization probably occurs in Ampullary Portion of Uterine Tubes
-One spermatozoon locks the door for other spermatozoa in Block to Polyspermy

Front 3

Phases of Oocyte penetration (3)

Back 3

1) In phase 1, spermatozoa pass through the corona radiata barrier
2) In phase 2, one of more spermatozoa penetrate the zona pellucida
3) In phase 3, one spermatozoon penetrates the oocyte membrane while losing its own plasms membrane

Front 4

Consequences of fertilization (5)

Back 4

-Triggers meiosis II in secondary oocyte -> ovum and 2nd polar body
-Block To Polyspermy
-Reestablishes Diploidy (zygote)
-Initiates Developmental Program
-Determines Genetic Sex

Front 5

Syngamy

Back 5

-Haploid Female Pronucleus and haploid Male Pronucleus share ovum cytoplasm
-They fuse (syngamy) to produce a single diploid Zygote Nucleus
-In about 24 hours, mitosis occurs -> two diploid Blastomeres forms (In humans, blastomere formation begins immediately following fertilization and continues through the first week of embryonic development. About 30 hours after fertilization, the egg divides into two cells. These mitotic divisions continue and result in a grouping of cells called blastomeres.)

Front 6

Cleavage

Back 6

-In next few days, several more cleavages occur, producing a conceptus consisting of many Totipotent Blastomeres (Totipotency is the ability of a single cell to divide and produce all the differentiated cells in an organism, including extraembryonic tissues)
-At first, blastomeres are loosely associated, looking like portions of a mulberry- called Morula (A morula (Latin "morus", mulberry) is an embryo at an early stage of embryonic development, consisting of approximately 12-32 cells (called blastomeres) in a solid ball contained within the zona pellucida.)

Front 7

Compaction (Trophoblasts and Embryoblasts)

Back 7

-Individual blastomeres have changes in cell surface chemistry and they now adhere strongly to one another
-This creates an outer and an inner population of cells
-Both populations continue to divide, producing Trophoblast (Trophoblasts (from Greek threphein: to feed) are cells forming the outer layer of a blastocyst which provide nutrients to the embryo and develop into a large part of the placenta.) and Embryoblast (the inner cell mass is the mass of cells inside the primordial embryo that will eventually give rise to the definitive structures of the fetus.)

Front 8

Early blastomeres and totipotency

Back 8

-Removal of early blastomeres still results in formation of complete fetus-blastomere biopsy possible for prenatal genetic manipulations
-Dyes injected into one of four blastomeres end up in both trophoblast and embryoblast
-Therefore, early blastomeres are totipotent

Front 9

In Vitro Fertilization I

Back 9

You have a patient with scarring and blockage of uterine tubes but otherwise healthy
Couple will experience infertility
Woman can be hormonally primed to multiple ovulation events in single cycle and secondary oocytes can be collected
Eggs and sperm mixed in culture dish in laboratory

Front 10

In Vitro Fertilization II (risks)

Back 10

After fertilization, several early embryos are collected and transferred into uterus via canula
Woman can then become pregnant and deliver a normal baby
Risks
-Multiple Pregnancies
-None for increased incidence of birth defects

Front 11

Other ARTs (Assisted Reproductive Technology) (5)

Back 11

-Artificial insemination from donor
-Egg donation
-Surrogate mothers
-Screening for genetic defects
-Sex selection